1. Field of the invention
This invention relates to iodine-containing surface active compositions, useful for cleansing and degerming skin, possessing cosmetically appealing properties such as high lather, good emolliency, mildness, and a pleasant afterfeel, and also to iodine-containing compositions useful for cleaning and degerming hard surfaces, possessing good detergency and long-lasting biocidal activity.
Iodine-containing preparations are known to be excellent germicides in that they will kill rapidly a broad spectrum of bacteria and viruses. However, previously known surfactant or polymeric complexing agents for iodine must be formulated with additional surfactants to make products suitable for hand washing or more general human cleansing problems, because they lack cosmetic appeal in that they are not superior lathering and foaming compositions, they lack emolliency, and in most cases are irritating to skin. An object of our invention is an iodophor that possesses good lather, emolliency, and mildness in and of itself.
It is not possible with previously known iodophors to formulate products with low levels of iodine for use without dilution in products such as douches, because at low levels of both iodine and complexing agent the iodine has a high vapor pressure, and if more complexing agent is added the iodine is unstable. It is a further object of this invention to provide formulations with low iodine vapor pressure and stable iodine at very low levels of iodophor so that they will have the cosmetic appeal of less intense colors, and a broader range of useful concentrations.
Previously known iodophors have limited shelf life because the iodine continues to react, however slowly, regardless of the age of the product. Another object of this invention is a product with a greatly extended shelf life because an equilibrium level of iodine is reached which does not change on storage.
Iodophors used as hard surface detergents usually contain ethoxylated surfactants as the iodine carrier. When these detergents are diluted to 25 to 50 ppm iodine, the iodine is no longer associated with the ethoxylated surfactant and reacts rapidly with any organic matter present and is destroyed. It is a further object of this invention to provide formulations in which the iodine remains associated with the surfactant at high dilutions so that the stability of the iodine in the presence of organic matter is improved while the biocidal activity remains high.
2. Description of the prior art
Iodophors suitable for use as biocidal cleaners of hard surfaces are well known articles of commerce. They are iodine "complexes" made from nonionic surfactants of the type EQU R-(O-CH.sub.2 CH.sub.2).sub.n -OH
where n.times.44=approximately 60 percent or more of the molecular weight of the surfactant molecule, or EQU H(OCH.sub.2 CH.sub.2).sub.n -O-(C.sub.3 H.sub.6 -O).sub.o -(CH.sub.2 CH.sub.2 O).sub.m H
where (m+n).times.44=20 percent or more of the molecular weight of the surfactant molecule. Many such examples occur, for instance in U.S. Pat. Nos. 3,028,299 and 2,971,777. However, nonionic surfactants of the above type of themselves are not suitable for hand washing products because they do not lather and lack emolliency. When diluted for use as hard surface cleaners the iodine vapor pressure is greatly increased, making the iodine in the diluted solutions unstable.
Ethoxylated amines and quaternized ethoxylated amines (U.S. Pat. Nos. 3,028,299 and 3,539,520) have been used both by themselves and in combination with nonionic surfactants to complex iodine. These amines and quaternaries contain at least 15 ethyleneoxy groups so that the condensed ethylene oxide represents a substantial portion of the molecule, and thus have the poor cosmetic properties of the nonionic surfactants. Iodophors of quaternary ammonium salts that do not contain condensed ethylene oxide are disclosed in U.S. Pat. No. 2,679,533. These iodophors tend to precipitate and are not suitable for extended storage.
Polyvinylpyrrolidone is used to make iodophor powder concentrates (U.S. Pat. Nos. 2,706,701; 2,900,305; and 3,028,300). They require the addition of lathering and/or detergent surfactants to make products for topical or hard surface cleaning. Nor can they be diluted extensively without an unacceptable rise in iodine vapor pressure.
Acid is traditionally added to iodophors (U.S. Pat. Nos. 3,029,183; 3,308,014; 2,977,315; and 3,274,116). Iodine is most biocidal at pH values below 4 so sufficient acid is added to reduce the pH to this value in the product as used. Beyond this acid may be added to assist cleaning (as in removing milkstone in dairy equipment). Organic acids such as hydroxyacetic acid can help solubilize the iodophor in some instances.
Iodophors have been prepared from equimolar mixtures of ethoxylated amine oxides and iodine (U.S. Pat. No. 3,534,102). Ethoxylated amine oxides with about 15 moles of condensed ethylene oxide or more are similar to nonionic surfactants in that they do not lather and lack emolliency. Amine oxides with only two moles of condensed ethylene oxide, when reacted with a molar equivalent of iodine are water insoluble. Without any added acid the products lack shelf stability.
Columns or beds of strongly basic anion exchange resins containing combined triiodide have been used to disinfect water (U.S. Pat. Nos. 3,817,860 and 3,923,665). Such compositions are not suitable for liquid cleaning products in that they are insoluble beads.
Amphoteric surfactants containing amine or quaternary ammonium groups, and sulfate or carboxylate groups have been used to prepare iodophors (U.S. Pat. No. 3,380,923). Such products tend to precipitate unless either a substantial amount of nonionic surfactant is present or the amphoteric surfactant itself contains condensed ethylene oxide. They also have high iodine vapor pressure on dilution.
Amine oxides are commonly used in shampoos and other detergent products (U.S. Pat. Nos. 3,808,311; 4,133,779; 4,065,409; 3,959,157 and numerous others). They are known to be mild to skin and possess good detergency. They are usually used at pH values above about 5 so that they are compatable with anionic detergents.